The present invention relates to rotary contactors, in particular for motor vehicles, of the kind comprising two coaxial parts which are mounted for movement in rotation of one with respect to the other against a flexible tape providing electrical connection and wound between the said parts by being attached at one of its ends to one of the said parts and at its other end to the other said part.
Such a contactor is described for example in the French patent application filed on the Sep. 7, 1995 under the number 95 10 691 and published under the number 2 738 677.
As is well known, the flexible tape includes one or more electrical conductors and an insulator for insulating the conductors from each other, and provides electrical connection between the two parts without microswitching.
The rotary contactor provides electrical connections for the purpose of, for example, controlling an inflatable air bag for the protection of the driver, or for controlling the horn from the steering wheel.
With this type of contactor a problem arises because it is necessary to be able to perform for example 2.5 turns of the steering wheel in one direction and 2.5 turns of the steering wheel in the other direction.
Thus the tape winds and unwinds, and has to be of great length in order to satisfy rotation of the order of 5 turns which is necessary in most motor vehicles, this rotation being limited by end stops or by the tension in the tape.
The length of the tape is therefore variable according to the winding and unwinding diameters; in general terms, the length of these tapes is of the order of 3 to 6 meters, and this contributes to the cost of the rotary contactor to a considerable extent, especially having regard to the number of paths or conductors provided by the tape.
It is equally desirable to reduce the radial size of such a contactor installed below the steering wheel in a location close to numerous electrical devices such as switches.
In practice, the internal diameter of the hub is a function of the diameter of the steering shaft which extends through the fixed steering column of the vehicle, which therefore dictates the value of the hub diameter.
It has been proposed in the above mentioned Application to provide a rotary contactor in which one of the parts comprises a rotatable hub and the other part a fixed hollow housing, the said contactor including, firstly, a rotor mounted for rotation in the housing, and secondly, an epicyclic gear train carried by the housing and by the hub and the rotor, for driving the rotor in rotation through the hub and for reducing the number of turns between the hub and the housing, the rotor having passage means for the flexible tape and carrying, for rotation on the rotor, a pinion adapted to mesh with a set of teeth formed in the interior of the housing and a set of teeth formed on the hub on the outside of the latter.
If the reduction in length of the tape and in the size of the contactor is obtained with a contactor of this type, the presence of an epicyclic gear train involves the risk of making such a contactor noisy.